01 - Place the chopped dark chocolate in a heatproof bowl.
02 - Heat the heavy cream in a small saucepan over medium heat until it just begins to simmer; avoid boiling.
03 - Pour the hot cream over the chopped chocolate, let sit for one minute, then gently stir until smooth and fully melted.
04 - Add the cubed butter and stir until the mixture is glossy and uniform.
05 - Cover with plastic wrap and refrigerate for 1 to 2 hours until firm but scoopable.
06 - Scoop portions of the chilled mixture using a teaspoon or melon baller and quickly roll into balls between your palms.
07 - Roll each truffle in cocoa powder to achieve an even coating.
08 - Arrange truffles on a parchment-lined tray and refrigerate at least 30 minutes before serving.